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Turbulent drag reduction by anisotropic permeable coatings

Gomez-De-Segura, G and Sharma, A and Garcia-Mayoral, R (2017) Turbulent drag reduction by anisotropic permeable coatings. In: UNSPECIFIED.

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Abstract

The behaviour of turbulent flow over anisotropic permeable substrates is analysed numerically through linear stability analysis and Direct Numerical Simulation (DNS). The flow within the permeable substrate is modelled by the Brinkman equation, which is solved analytically to obtain the boundary conditions at the substrate-channel interface for both the DNS and stability analysis. The linear stability analysis is used as an a priori model to capture the onset of drag-increasing Kelvin-Helmholtz rollers. The associated instability is essentially driven by the wall-normal permeability K . DNS corroborates that the drag decreasing effect of slip is offset by the drag increasing effect of the wall-normal transpiration. The latter is associated with the presence of large spanwise rollers. When permeable substrates are considered, the transpiration is wavelength-dependent, and inhibits the formation of large spanwise structures of wavelengths λ ≈ 250, thereby reducing the negative impact. + + y x

Item Type: Conference or Workshop Item (UNSPECIFIED)
Subjects: UNSPECIFIED
Divisions: Div A > Fluid Mechanics
Depositing User: Cron Job
Date Deposited: 28 Nov 2017 01:44
Last Modified: 15 Apr 2021 06:07
DOI: